1. Geographic Coordinates (Latitude And Longitude, or Lat/Long)
Distance for 1 minute (1/60 degree) of longitude (E-W) at 40 deg. latitude is 0.88 mile.
Distance for 1 minute latitude (N-S) is 1.15 mile.

2. Universal Transverse Mercator (UTM)
Distance is measured in kilometers north and south from the equator and east and west from the "principal meridian," located in the Pacific Ocean near the International Dateline.
The UTM system divides the world into a regular nonoverlapping grid of quadrangles, called zones, each each 6° degrees of longitude wide and 8° of latitude high.

Notation: eg UTM: 18T E 529985 N 4505432
Zone 18T
Which is the distance in meters from the lower left of our zone. See map below. I'll fool around with my gps to see if I can get it to show UTM. And find a Long/Lat to UTM converter to compute the final location in UTM. It would be easier because you know how many meters off you are.

3. Public Land System (Township And Range, or T&R)

Map Datums
All new maps use the WGS84 datum.

Links:
Map, Compass and GPS Skill
Sample map
GPSs
US Public Land Survey System (PLSS) - Township and Range